%File: VAD.tex
%Date: Tue Dec 31 01:12:04 2013 +0800


\section{VAD}
\begin{frame}{VAD}
  \textbf{Voice Activity Detection} shall be applied for all signals as a pre-filter.
  We've tried 2 different approaches:
  \pause
  \begin{itemize}
    \item Energy-Based:
      \begin{itemize}
        \item Filter out the intervals with relatively low energy.
        \item Work perfectly for high-quality recordings.
        \item Sensitive to noise.
      \end{itemize}
      \pause

    \item Long-Term Spectral Divergence
      \begin{itemize}
        \item Compare long-term spectral envelope with noise spectrum.
        \item More robust to noise, used in our GUI.
        \item
            \footnotesize\it\color{red!50!black}
            Efficient voice activity detection algorithms using long-term speech information,
            Ramırez, Javier, 2004
      \end{itemize}
  \end{itemize}
\end{frame}

\begin{frame}{LTSD}
  \begin{center}
    \includegraphics[width=0.7\textwidth]{res/ltsd.png}
  \end{center}
\end{frame}
